Magnetic properties of large-scaled MnBi bulk magnets

Kim, Sumin,Moon, Hongjae,Jung, Hwaebong,Kim, Su-Min,Lee, Hyun-Sook,Choi-Yim, Haein,Lee, Wooyoung Elsevier 2017 Journal of alloys and compounds Vol.708 No.-

<P><B>Abstract</B></P> <P>We investigated the magnetic properties of large, compacted, sintered MnBi bulk magnets with dimensions of 20.3 × 15.3 × 10.3 mm<SUP>3</SUP>. To obtain a high content of the low-temperature-phase (LTP) of MnBi in the precursor powders, a new process was implemented and produced about 98 wt% of LTP. To improve the coercive field of MnBi, particle sizes were controlled using different milling techniques. The dependence of magnetic properties of the bulk magnets on the particle size was analyzed. The highest maximum energy product, (<I>BH</I>)<SUB>max</SUB>, obtained among our samples was 7.3 MGOe. This is the first report of demonstrating high performance in large-sized MnBi bulk magnets.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MnBi has a great potential as a rare-earth-free permanent magnet that can be used in high temperature (∼200 °C) applications. </LI> <LI> High performance in large-sized MnBi bulk magnets is reported for the first time. </LI> <LI> High-quality precursor powders were prepared by combining new procedures of cold-pressing and magnetic separation. </LI> <LI> Magnetic properties of bulk magnets were controlled using different milling techniques. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

YBCO 초전도 벌크 합성

이상헌 ( Sang Heon Lee ) 한국전기전자재료학회 2024 전기전자재료학회논문지 Vol.37 No.4

In this study, we fabricated single grain YBCO bulk superconductors with control of the distance between the seed and the upper surface of the YBCO compacts. The magnetic levitation force of the YBa₂Cu₃O₇ superconducting bulk, which corresponds to the energy amount of the superconducting bulk, was measured to be 32.634 N at the center of the bulk where the seed was placed. Under field cooling conditions, a capture magnetic force of 2.17 kG was observed at the center of the bulk. The trapped magnetic force curve corresponding to the stability of the superconducting bulk means that the superconducting specimens were well grown in the form of single grains.

A comparative analysis of the superconducting bulk and wire types applicable to mechanical DC circuit breaker

Sang-Yong Park(박상용),Hyo-Sang Choi(최효상) 대한전기학회 2021 전기학회논문지 Vol.70 No.10

The core technology of the DC grid system is to protect the system in the event of a transient and to cut-off the faults current in a trouble line, quickly. We sat down to analyze to implement the DC breaking technology of mechanical DC circuit breaker on the faster and more safely. However, the mechanical DC circuit breakers have limitations on the opening speed and the components of the break contact. To solve this problem, we applied a superconducting electromagnet to a mechanical DC circuit breaker and proposed a method to reduce the DC Arc energy generated during the breaking operation. In this paper, we proposed the application of superconducting bulk-type magnet and superconducting wire-type electromagnet to the conventional mechanical DC circuit breaker and analysed the breaking characteristic. We designed a mechanical DC cutting-off contact, a superconducting bulk-type magnet, and a superconducting wire-type electromagnet through the Maxwell 3D program. As a result, the Lorentz force was generated between the mechanical DC cutting-off contacts each applied the superconducting bulk-type magnet and wire-type electromagnets. The superconducting bulk-type magnets produced a magnetic force of about 269.3 A/m and the superconducting wire-type electromagnet produced a magnetic force of about 610 A/m affecting DC arc blowing.

A study on design process of HTS bulk magnet synchronous motors

Jaheum Koo,JuKyung Cha,Jonghoon Yoon,Seungyong Hahn 한국초전도저온학회 2024 한국초전도저온공학회논문지 Vol.26 No.1

This study explores the use of a bulk type high-temperature superconductors (HTS) as trapped field magnets in synchronous motors. A HTS bulk is examined for its ability to generate powerful magnetic fields over a permanent magnet and to eliminate the need for a direct power supply connection compared to a tape form of HTS. A 150 kW interior-mounted bulk-type superconducting synchronous motor is designed and analyzed. The A-H formulation is used to numerical analysis. The results show superior electrical performance and weight reduction when comparing the designed model with the conventional permanent magnet synchronous motor of the same topology. This study presents HTS bulk synchronous motor’s overall design process and highlights its potential in achieving relatively high power density than conventional permanent magnet synchronous motor.

와상전류를 응용하여 지진 충격흡수 장치를 위한 초전도 자기부상 안정화 향상

장형관,송준후,아시프 마흐무드,김세빈,양찬호,성태현,Jang, Hyung-Kwan,Song, Daniel,Mahmood, Asif,Kim, Se-Bin,Yang, Chan-Ho,Sung, Tae-Hyun 한국초전도학회 2011 Progress in superconductivity Vol.12 No.2

Pinning force is the mechanism between a superconductor and a permanent magnet and it provides a stable levitation. However, when external force greater than the pinning force such as the earthquake exerts, the levitated object may lose the levitating characteristic. In order to achieve more stabilized levitation, the copper plate was inserted in between a superconductor and permanent magnets. And by applying the eddy current effect caused from the relationship between a copper plate and permanent magnets, more stabilized levitation can be established. In this study, an optimized design was found based on various configurations of permanent magnet's polarity, thickness and area of copper plate, and the gap distance between copper plate and permanent magnet. As results, higher eddy current value was obtained at where the change of polarity exists in permanent magnet configuration, and the highest eddy current value was observed at the copper plate thickness of 5 mm and the area of 80 mm ${\times}$ 80 mm. From the resulted optimized conditions above, which are 7 mm gap distance between a superconductor and permanent magnets and 80 mm ${\times}$ 80 mm ${\times}$ 5 mm dimension of a copper plate, the stiffness value was 65 % increased comparing to without any copper plate insertion.

시간 경과에 따른 YBCO 초전도 복합체의 포획 자기장 감쇄

이만수,장건익,전병혁,하동우,손명환,한영희,박병준,Lee, M.S.,Jang, G.E.,Jun, B.H.,Ha, D.W.,Son, M.H.,Han, Y.H.,Park, B.J. 한국초전도학회 2011 Progress in superconductivity Vol.12 No.2

We studied the trapped field properties of bulk Y-Ba-Cu-O superconductors by applying 3 T of the permanent or $Nb_3Ti$ superconducting magnet. The 28 mm circular type of YBCO bulk superconductor was prepared and then hole at the center of bulk, parallel to the c-axis, was mechanically drilled. Typical size of hole in YBCO bulk was 10 mm in diameter. In order to examine the trapped field variation in terms of different impregnated materials, a hole in YBCO bulk was filled with resin and indium respectively. The trapped field decay due to flux flow was determined in terms of time. Our preliminary result indicates the trapped field value measured on the YBCO without hole after 30 minute by applying 3 T, was 6,500 G, which is much higher than that, 4,500 G, measured on YBCO with hole. Also, we confirmed that the tendency of a trapped field decrement with time was almost the same regardless of the impregnated materials in YBCO.

Rare-Earth-Free MnBi Permanent Magnets: Bulks and Thin Films

Hyun-Sook Lee,Sumin Kim,Hongjae Moon,Hwaebong Jung,Wooyoung Lee 한국자기학회 2023 한국자기학회 학술연구발표회 논문개요집 Vol.33 No.1

Magnetic field distribution in steel objects with different properties of hardened layer

Byzov, A.V.,Ksenofontov, D.G.,Kostin, V.N.,Vasilenko, O.N. Techno-Press 2022 Advances in computational design Vol.7 No.1

A simulation study of the distribution of magnetic flux induced by a U-shaped electromagnet into a two-layer massive object with variations in the depth and properties of the surface layer has been carried out. It has been established that the hardened surface layer "pushes" the magnetic flux into the bulk of the magnetized object and the magnetic flux penetration depth monotonically increases with increasing thickness of the hardened layer. A change in the thickness and magnetic properties of the surface layer leads to a redistribution of magnetic fluxes passing between the poles of the electromagnet along with the layer and the bulk of the steel object. In this case, the change in the layer thickness significantly affects the magnitude of the tangential component of the field on the surface of the object in the interpolar space, and the change in the properties of the layer affects the magnitude of the magnetic flux in the magnetic "transducer-object" circuit. This difference in magnetic parameters can be used for selective testing of the surface hardening quality. It has been shown that the hardened layer pushes the magnetic flux into the depth of the magnetized object. The nominal depth of penetration of the flow monotonically increases with an increase in the thickness of the hardened layer.

3 T급 대면적 YBCO 초전도 벌크자석 개발

한상철,정세용,박병준,한영희,Han, S.C.,Jeong, S.Y.,Park, B.J.,Han, Y.H. 한국초전도학회 2012 Progress in superconductivity Vol.14 No.1

For the practical application of a YBCO superconductor bulk magnet, the superconductor bulk magnet with strong and stable magnetic field on a large area surface should be fabricated. To satisfy these requirements, we have designed a conduction-cooled bulk magnet system using six single grain YBCO bulk superconductors. Six rectangular-shaped YBCO bulk superconductors with a dimension of $38{\times}38{\times}15mm^3$ were field-cooled at 20 K using a superconductor magnet with maximum operating magnetic field of 4 T. The magnetic flux of 3.0 T and 2.8 T were achieved on the surface of bulk superconductors and over the vacuum chamber surface of the refrigerator, respectively.

벌크형 초전도체의 전기자기적 특성

이상헌,Lee, Sang-Heon 한국전기전자재료학회 2017 전기전자재료학회논문지 Vol.30 No.2

In this research, the development of fabrication technique of bulk YBaCuO superconductors for application was studied. In fluence of $BaZrO_3$ addition on magnetization characteristics of thermal pyrolysis textured YBaCuO superconductor was investigated. Fine $BaZrO_3$ particle were dispersed within the textured YBaCuO matrix by means of the thermal pyrolysis processing. Magnetic levitation force for YBaCuO superconductors were obtained using Nd-B-Fe permanent magnet, at 77 K and at the magnetic field from 0 to 5.3 K gauss. In the unadded superconductor and 5 wt% $BaZrO_3$ addition, anomalous magnetization behavior, which is characterized by the intermediate magnetic field, was observed at 77 K. Critical current density was about few hundreds $A/cm^2$ and the magnetic characteristics increased slightly by addition of $BaZrO_3$ powder. Maximum magnetic force was obtained in the YBaCuO superconducting bulk with 3 wt.% $BaZrO_3$ addition.